Full: If it hits, this attack strikes for +5...17 damage. If you targeted a foe who had less Health than you, that foe and all adjacent foes are struck for 15...51cold damage.
Concise: Deals +5...17 damage. Deals 15...51cold damage to target and adjacent foes if you targeted a foe with less Health than you.
The conditional damage will not trigger if your target dies due to the non-conditional damage.
The conditional damage will trigger (providing conditions are met) even if the initial attack misses or is blocked. This can be used in combination with Intimidating Aura to disenchant foes.